Photographic enlarger with automatic focus



June 9, 1959 UZ 2,889,741

PHOTOGRAPHIC ENLARGER WITH AUTOMATIC FOCUS Filed April 1'7, 1957 5Sheets-Sheet l V Flg/ mooooow IN V EN TOR.

FHOTOGRAPHIC ENLARGER WITH AUTOMATIC FOCUS Filed April 1'7, 195'? C. LUZ

June 9, 1959 3 SheetsQ-Sheet 2 June 9, 1959 2,889,741

PHOTOGRAPHIC' ENLARGER WITH AUTOMATIC FOCUS Filed April 17, 1957 C. LUZ

3 Sheets-Sheet 3 Fig.5

Q0 0 0 cM/ 4 INVENTOR.

PHOTOGRAPHIC ENLARGER WITH AUTOMATIC FOCUS States Patent Christian Luz,Wetzlar (Lahn), Germany, assignor to Ernst 1 This invention relates tophotographic enlargers of the type in which the photographic enlargingunit or head is vertically adjustable in relation to the plane ofproduction or to a printing board which is placed upon the base board ofthe enlarger. The photographic enlarging unit or head is raised orlowered by means of arms which are pivotally connected to and betweenthe enlarging head and a supporting stand, these arms forming oppositesides of a parallelogram. The sharp focusing of the enlarger objectivesis accomplished by certain steering cams and cam rollers which areoperatively connected with the objectives and one of the arms.

Prior devices of this type are not entirely satisfactory because ofunfavorable load and wear conditions at the points where the combinedactions of the steering cams and cam rollers are carried over to theobjectives for focusing purposes. Again, such prior devices are notsuitable for use in enlargers which are provided with exchangeableobjectives of different focal lengths where the objectives are focusedby automatic operation of the steering cams, the steering cam rollersand associated parts.

The objects of this invention are to improve generally the constructionand operation of this type of enlarger, particularly in respect to theoperations of the steering cams and the cam rollers and the use ofobjectives of different focal lengths. Other objects of the inventionwill appear in the following specification read together with theaccompanying drawings in which:

Fig. 1 is a side view of a photographic enlarger embodying thisinvention, parts being broken away.

Fig. 2 is an enlarged detail view partly in section, showing themechanism for moving one of steering rollers axially so that it mayoperatively engage its steering cam when a certain objective is selectedfor use.

Fig. 3 is a diagrammatic view showing the steering cams, the steeringcam rollers and the objectives with associated parts.

Fig. 4 is a detail view showing the steering cams and their support.

Fig. 5 is a detail sectional view of a locking device.

Fig. 6 is a view illustrating a compensating load device.

Referring to Fig.1, the photographic enlarging unit or head includes anilluminating head 1, partly broken away, the negative stage 2 with adownwardly extending arm 2a and the objective carrier 3 which carriesthe objectives 4 and 5. The head is supported on a stand 8 by arms 6aand 6b and is adjusted vertically in relation to the base board 7 uponwhich a printing board, not shown, is placed by the operator. The arms6a and 6b form opposite sides of a parallelogram.

The objective carrier 3 with the objectives 4 and 5 slides vertically onthe fixed arm 2a so that either of the objectives may be moved into thecorrect optical enlarging position below the negative stage 2. In orderto move either of the objectives 4 or 5 into optical alinement with theoptical axis of the enlarger, the objectives are carried by atransversely movable slide to which is supported in the objectivecarrier 3, Fig. 3. The objectives are locked in enlarging positions by apawl 28, which is pivoted at 28b in the carrier 3 and the pawl extendsinto a recess 10a in the slide 10 and is held there by a spring 28a,Fig. 5. When the carrier 3 is moved upwards into contact with thenegative stage 2, an abutment 29 on the stage strikes the pawl 28 sothat it is lifted out of the recess 10a. The slide 16 is then releasedand may be moved transversely in the carrier 3 whereby to shift theobjectives. Stops 3a in the carrier limit the movements of the slide ineither direction and the objectives are thus automatically alined withthe optical axis of the enlarger.

The objective carrier 3 moves vertically on the fixed arm 2a by means ofa link 16, Fig. 1, which is pivoted on the carrier at 17. The otherlower end of the link is pivoted at 15 to a swingable roller arm 14which, in turn, is pivoted at 13 on one of the arms 6a and 6b. At thepivot 15 there may be a handle, not shown, for moving the enlarging headvertically. The swingable roller arm 14 carries two cam rollers. Oneroller 14a engages the steering cam 12. The other roller 14b is axiallymovable in a link 20, Fig. 2. The second roller 14b is retracted fromcontact with its steering cam 11 when the objective 5 is selected foruse. The roller 14b is projected to engage its steering cam 11 when theobjective 4- is selected for use.

Fig. 1 shows the roller 14a operatively engaging its steering cam 12whereby to steer the roller arm 14 and the link 16 to focus theobjective 5. Fig. 3 shows the one roller 14b within the hub of the link20 operatively engaging its steering cam 11 to steer the roller arm 14and the line 16 whereby to focus the objective 4. Fig. 1 shows theroller cam 14b retracted and out of engagement with the cam 11. In Fig.3 the roller 14b within the hub of the link 20 is projected intooperative engagement with its steering cam 11. The means for retractingand projecting the cam roller 14b is shown in Fig. 2 to which referenceis now made.

The roller arms 14 is formed with a hub 20 having a recess 14a. The hubcontains a bearing sleeve 20a. Within the sleeve there is an axiallymovable hollow shaft 21. A plug 21b closes one end of the shaft 21 whichcarries the cam roller 14b as shown. A pin 22 passes through the hub 20,the sleeve 20:: and openings 21a in the shaft 21 to prevent axialmovement of all parts except the shaft 21 and whereby to prevent turningof the parts. The pin carries an abutment 22a. Between the abutment andthe closing plug 211) there is located an expansion spring 23 which, byaction against the plug, tends to retract the shaft 21 into the hub andthus tends to keep the cam roller 14b withinthe recess 14c and out ofengagement with the steering cam 11.

A flexible cable 25, Bowden type, extends between the hub 20 and theslide N, Fig. 3. The cable carries a pusher pin 25a which engages theplug 21b to project, i.e. push, the shaft out of the recess intooperative engagement with the steering cam 11. Fig. 3 shows the roller14b in projected position in dotted lines. The other end of the cable 25ends in a pin 27 adapted to be struck by the slide it} when theobjective 4 is optically alined within the enlarger, Fig. 3. A screwcover 24 closes the end of the hub 20.

When the objective 4 is selected for use, the slide 10 is movedtransversely so as to strike the pin 27 and thus, via the cable 25, thecam roller 14b is projected to engage the cam 11. The objective carrier3 is then slightly lowered so that the pawl spring 28a may lift the pawlto enter the recess 10a and lock the parts in the new position.

The operation is as follows: As shown in Fig. 1 the objective is focusedand in enlarging position. In order to achieve this result, the camroller 14a operatively engages its steering cam 12 whereby, via theswingable roller arm Ltand the link 16, the objective is movedvertically into the correct position below the negative stage 2.

i f the other objective 4 is selected for use, the objective carrier 3is lifted to contact the negative stage 2 whereby, again via the link16, the swingable roller arm 14 is swung so far on its pivot 13 that thecam roller 14b can be projected into the space between the two steeringcams. In this position the abutment 29 on the stage 2 strikes the pawl28 and thereby releases the slide which can now be moved transversely tobring the objective 4 into alinement with the optical axis of theenlarger. The earn roller 14a will then no longer engage its steeringcam 12 whereas the other cam roller 1411 will engage its steering cam11..

if the objective 5 is again selected for use, the above operations takeplace in reverse order. First, the carrier 3 is lifted and the steeringcam roller 14b relieved of its load and thereafter, by the reversemovement of the slide 10, the cam roller 14b is retracted and the othercam rolier 14 1: engages the cam operatively to focus the objective 5.

The cams 3.1 and 12 are adjustably carried by a segment 2b of the fixedarm 2a as shown in Fig. 4. The cams are adjusted by means of anadjusting screw 34 located within an opening 32 in engagement with thecam. By rotating the screw 33 the other screw 34 is shifted to adjustthe cam on the support. The other cam 11 is adjustably secured inposition by screws 40 passing through slots 41. The cam is adjusted bymeans of a screw 44 acting against the cam and a spring 43 as shown.

The entire weight of the objective carrier with the two objectives restupon the steering cams. While this arrangement may suffice to balancethe loads, it is desirable to use an additional load balancing device asshown in Fig. 6. A load balancing spring 51 is contained within ahousing 50 supported on the arm 2a. The outer end of the spring is via acable 52 connected to the objective carrier 3. The spring is adapted tobe adjusted to balance the weight of the objective carrier and theobjectives.

The automatic focusing of the objectives is the result of the combinedaction of the steering cams and the cam rollers. The position of the camroller on the steering cam, herein described as operative engagement,focuses the selected objective in that thereby the objective is movedvertically by the link 16 into the required optical distance below thenegative stage, the pivot being moved, raised or lowered, when theappropriate steering cam roller operatively engages the steering cam.The change of objectives may be made irrespective of the level of theenlarging unit. The contact between the carrier 3 and the negative stage2 releases the transverse slide 10 so that the selected objective can bebrought into alined position with the optical axis of the enlarger. Asthe carrier 3 is slightly lowered from the negative stage 2, the camrollers, 14a or 1413, as the case may be, will operatively engage theirrespective steering cams as shown in Figs. 1 and 3 and the slide 19 isthen again locked in the carrier 3.

I claim:

1. In a photographic enlarger, in combination, a vertically movableenlarger unit, a support therefor, two arms forming opposite sides of aparallelogram pivotally connecting said unit with the said support,steering cams supporting means in said unit, an objective carriertherein engaging said steering cams supporting means in verticallyslidable relation thereto, two objectives of different focal lengthssupported in said objective carrier, means for moving either of saidobjectives into operative optical alinernent with the optical axis ofthe enlarger, means for focusing either of said objectives when it hasbeen moved into alined position as aforesaid comprising two steeringcams supported on said steering cams supporting means, a swingable camroller support pivoted on one of the said arms, two cam rollerssupported on said swingable support, one of said cam rollers beingadapted to operatively engage one of said steering cams when one of thetwo objectives is moved into optical alinement with the optical axis ofthe enlarger as aforesaid, the other of said cam rollers being adaptedto operatively engage the other of said steering cams when the otherobjective of the two objectives is brought into alined position asaforesaid, a link pivotally connecting said swingable cam roller supportwith said objective carrier for moving the cam roller support about itssaid pivot and causing either one of said cam rollers to operativelyengage its steering cam to move the objective carrier vertically in saidunit into a position in which the particular objective alined with theoptical axis of the enlarger is placed in enlarging position.

2. A photographic enlarger according to claim 1 including a loadcompensating device supported in said enlarging unit and operativelyconnected to said slidable objective carrier for relieving the said twosteering cams and the cam rollers from the weight of the objectivecarrier and the objectives thereon.

3. A photographic enlarger according to claim 1 including means forpreventing one of the said two cam rollers from operatively engaging itssteering cam when a predetermined objective is selected for use andmoved into its enlarging position and means for moving the said one camroller into operative engagement with its steering cam when saidpredetermined objective is moved out of its enlarging position andreplaced by the other selected objective in enlarging position.

4. A photographic enlarger according to claim 1 including means formoving one of said cam rollers axially to operatively engage itssteering cam in response to the movement of one of said objectives intooptical axial alinement with the optical axis of the enlarger and aspring for retracting the said one cam roller from engagement with itssteering cam when the other of said objectives is moved into enlargingposition in the enlarger.

5. A photographic enlarger according to claim 1 including means foradjustably supporting the said two steering cams on the said camsupporting means.

6. In a photographic enlarger, in combination, a vertically movableenlarging unit, a support therefor, arms forming opposite sides of aparallelogram pivotally connecting said unit with said support, anobjective carrier in said unit to move vertically therewith, a slidetransversely movably supported in said carrier, two objectives ofdilferent focal lengths supported in said slide to be selectively movedby the slide into optical axial alinement with the optical axis of theenlarger, a spring pressed pawl in said slide for locking the slide tothe objective carrier when a particular objective has been moved intoalined position as aforesaid and means in the unit for moving said pawlout of locking engagement with the slide and unlock the slide from theobjective carrier just prior to the transverse movement of the slide inthe carrier in order to bring the other objective into alined enlargingposition in the enlarger.

7. A photographic enlarger according to claim 6 including a negativestage in the enlarging unit above the said objective carrier with itstransverse movable slide, a locking device interposed between theobjective carrier and the slide therein for locking the slide to theobjective carrier when a selected objective in the slide has been alinedwith the optical axis of the enlarger and means on said negative stagefor operating the said locking device to release the slide so that theslide may be transversely moved only when the other objective isselected for use.

References Cited in the file of this patent UNITED STATES PATENTSHopkins Apr. 5, 1927 Luz June 9, 1936 Leitz et a1. July 12, 1938 MederMar. 4, 1941 FOREIGN PATENTS Germany May 31, 1941 France Apr. 1, 1953

